furnace regulator system



E. LEHR.

FURNACE REGULATOR SYSTEM.

APPLICATION FILED MAR. 19. 1919.

lNVENTOR dw/fl Le/rr' WITNESSES:

ATTORNEY E. LEHR.

TURNACE REGULATOR SYSTEM.

APPLICATION FILED MAR. 19.1919.

1,320,071 Patented Oct. 28,1919.

2 SHEETSSHEET 2- WITNESSES: INVENTOR m/a. WMZ ATTORNEY v UNITED STATES PATENT o FIoE.

EDWIN LEHR, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOB TOWESTINGHOUBE ELEC- TRIO 8t MANUFACTURINGOOMPANY', A CORPORATION OF PENNSYLVANIA.

FURNACE-REGULATOR SYSTEM. I

Specification of Letters Patent. I

Patented Oct. 28, 1919.

Application filed newline, 1919. sum No. 283,625.

To all whom it may concern:

Be it known that I, EDWIN LEHR, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Furnace-Regulator Systems, of which the following is a specification.

My invention relates to regulator systems and particularly to regulator systems for governing the operation of electric furnaces.

One object of my invention 1s to provide a furnace-regulator system that shall be controlled either manually or automatically to maintain a substantially constant current flow through, or to maintain a substantially constant power input into, or to maintain a substantially constant voltage across, a furnace in asimple and an economical manner, without any abrupt circuit changes.

In operating electric furnaces, and particularly in operating electric furnaces that are provided with resistors having negative temperature coefiicients, it is essential to guard against overheating the furnaceby reason of any abnormal current flowlng through the resistors. Thus, in case the load on a furnace is reduced and the heat taken by radiation from the furnace resistor is reduced, then the ,7 resistor, by reasoirof 1ts having a negative temperature coefficlent, 1s liable to become overheated and permit an excessive current flow through the furnace Moreover, it is very desirable, in operating an electric furnace, to change the current flow through, or the power input into, the furnace without breaking the furnace circuit and without any abrupt circuit change.

In a furnace-regulator system constructed inaccordance with my invention, means is provided for governing the power lnput into the furnace, either manually or automatically, in accordance with the current flowing through the furnace, in such manner as to insure against overheating of the furnace and, moreover, means is provided for varying the power input into the furnace without causing any breaks or abrupt changes in the furnace circuit.

The furnace-regulator system utilized for practising my invention embodies a main' transformer provided with a secondary winding connected to the furnace resistor and a primary winding having one termlnal connected to one side of the supply circuit and a plurality of taps which are selectively connected to the other side of the supply circuit by means of an auxiliary transformer. The system is further provided with a selector switch, an induction regulator, and a suitable transfer switch.

The auxiliary transformer comprises a primary winding and a secondary winding having two coils each of which has one terminal thereof successively connected, by the transfer switch, to one side of the supply circuit. The selector switch serves toconnect the other terminal of the two secondary coils of the auxiliary transformer to selected taps extending from the primary winding of the main transformer. The induction regulator is energized by the main transformer and is so connected to the primary winding of the auxiliary transformer as to control the voltage which is impressed on the two secondary coils of the auxiliary transformer.

The selector switch, the transfer switch and the induction regulator are cared to an electric motor so that the trans er switch and the revolving parts of the induction regulator makeone complete revolution during the time the arms of the selector switch are erably operated in a forward and in a reverse direction under the control of two relays. The relays may be controlled either manually, by means of push buttons, or automatically, by a main control magnet, which is energized in accordance with the current flowing through the furnace.

In transferring the supply-circuit connection from one primary tap of the main transformer to a second tap in order to change the power input into the furnace, the transfer switch is first adjusted to a predetermined position for connectin one sec ondary coil of the auxiliary trans ormer to a contact arm of the selector switch, and the induction regulator is adjusted to a position for impressing a zero voltage on the two secondary coils of the auxiliary transformer. The voltage impressed on the two secondary coils of. the auxiliary transformer is increased to a value equal to one half the voltage existing between two adjacent primary taps of the main transformer, and then the two secondary coils of the auxiliary trans- .former are connected, in series and in opposition to each other, across two adjacent primary taps and to one side of the supply 011- cuit. Next, the first secondary C011 and the first rimary tap are disconnected from the supp y circuit by the transfer switch, leaving the second coil of the auxiliary transformer and the second tap of the main transformer connected to the supply circuit. At this time, the second coil of the secondary winding of the auxiliary transformer has a voltage impressed on it in opposition to the supply circuit voltage which is equal to onehalf the voltage existing between two adjacent primary taps of the main transformer. Finally, the voltage impressed on the second coil of the auxiliary transformer by the induction regulator is reduced to zero value so that the second tap of the primary winding is practically connected directly to the supply circuit.

Thus, the change of the supply-circuit connection from one transformer tap to an adjacent transformer tap is effected in a gradual manner to prevent any abrupt changes in the transformer circuit and, accordingly, in the furnace circuit which is connected to'the transformer.

In the accompanying drawings, Figure 1 is a diagrammatic view of a furnace-regulator system embodying my invention, and Figs. 2 and 3 are, respectively, side elevational and plan views of the induction regulator, the main transformer and the drum switch shown in Fig. 1 of the draw- Tteferring to the drawings, an electric furnace 1, having a heating resistor 2, is directly connected to the secondary winding 3 of a main transformer 4.. The main transformer 4 is provided with an auxiliary winding 7 and a primary winding 5, which is divided into two portions 6 and 8. The primary winding 5 is adapted to be connected across a supply circuit, comprising conductors 9 and 10, by means of a transfer switch 11, a selector switch 12, an auxiliary transformer 13 and an induction regulator 14. The transfer switch 11 embodies a contact segment 15, which engages a contact finger 16 at all times, and a contact segment 17, which is electrically connected to the contact segment 15 and extends slightly more than half-way around the drum upon which the segments 15 and 17 are mounted. The contact segment 17 is adapted to engage two contact fingers 18 and 19 for a purpose to be hereinafter set forth. The auxiliary transformer 18 embodies a primary winding 20 which is connected to the stationary coil 21 of the induction regulator 14, and a secondary winding comprising two coils 22 and 23. If so desired, the auxiliary transformer may be dispensed with and the coils 22 and 23 be embodied as a part of the induction regulator 14.

The selector switch 12 embodies two arms 24 and 25 which are cared together in any suitable manner an respectively, successively engage contact fingers 26 to 30, inclusive, and contact fingers 31 to 35, inclusive. The induction regulator 14 comprises the stationary coil 21, which is connected in series with the primary winding 20 of the auxiliary transformer 13, and a movable coil 36, which is connected in series with the auxiliary winding 7 of the main transformer 4.

One terminal of the portion 6 of the primary winding 5 is directly connected to the supply conductor 10, and the other terminal of this portion of the primary winding is connected to the contact finger 16 of the transfer switch 11. The two contact fingers 18 and 19 of the transfer switch 11 are re-.

spectively connected to one terminal of the secondary coils 22 and 23 of the auxiliary transformer 13. The other terminals of the two coils 22 and 23 are respectively connected to the two switch arms 24 and 25 of the selector switch 12. The portion '8 of the primary winding 5 is provided with a plurality of taps 37 to 41, inclusive, which are respectively connected to the contact fingers 26 to 30, inclusive, and a plurality of taps 42 to 46, inclusive, which are respectively connected to the contact fingers 31 to 35, inclusive.

The induction regulator 14, the transfer switch 11 and the selector switch 12 are operated by any suitable motor, such as a threephase induction motor 47, which is adapted to be connected across a supply circuit comprising conductors 48, 49 and 50 by means of two relays 51 and 52 for operation in a forward and in a reverse direction. The two relays 51 and 52 are adapted to be controlled manually by means of two push buttons 53 and 54, or automatically, in accordance with the current supply to the furnace 1 by means of a main control magnet 55. A double-throw, single-pole switch 56, comprising a switch blade 57 and two con tact fingers 58 and 59, is provided for connecting the two relays 5'1 and 52 for manual operation by the two push-buttons or for automatic operation by means of the main control magnet 55. When the switch blade 57 is connected to the contact finger 58, as illustrated in the drawing, the two relays 51 and 52 are under the control of the main control magnet 55, and when the switch blade 57 is in engagement with the contact finger 59, the two relays 51 and 52 are under the control of the push buttons 53 and 54. The relay 51 serves to connect the motor 47 across the supply conductors 48, 49 and 50 in order to effect rotation of it in a counterflowing through the furnace 1; The winding 61 o erates a core armature 63 which is pivota ly connected to a contact arm 64. The contact arm 64 is adapted to engage a main contact finger 65 for operating the relay'51 in one osition of the main control magnet 55 an to engage a main contact finger 66 for operating the relay 52 in the .opposite position of the main control magnet 55. The main control magnet 55 is adapted to be disengaged from the current transformer 62 by means of a switch 67 and the supply circuit, comprising conductors 9 and 10, is adapted to" be disengaged from the furnace system by means of a switch 68.:

In the operation of my furnace system,

---=it =is-essential rotate the; moving parts of the transfer switch ""11 and the induction regulator 14 at the same speed and to move the switch arms 24 and 25.of.the selector switch 12 from one contact finger to a' second contact finger during each revolution of the moving parts of the transfer switch and of the induction regulator. One means whereby the above operation of the transfer arrangement of gears and rods for obtaining the same sequence of operation of the various parts may-be utilized, if so desired.

Referring to Figs. 2 and 3 of the drawings, the movable coil 36 of the induction regulator 12 is mounted upon a rod 75 which is directly connected to the motor 47 in any suitable manner, as by means of the worm gearing 76. The rod 75 at the upper end thereof is provided with a double bell crank 77 which, in turn, is connected to two side rods 78- and 79.

The two contact segments 15 and 17 of the transfer switch 11 are mounted upon a contact drum 80 which, in turn, is mount edupon a shaft 81. The shaft'81 is provided with a double bell crank 82, which is similar to the bell crank 77 mounted upon the shaft 75, and is connected to the side rods 78 and 79. The two switch arms24 and 25 of the selector switch.12 are preferably mounted above the main transformer 4 and within the casing 83 which incloses der to be operated by the motor 47.

By the above connection, it is apparent that the drum 80 of the transfer switch 11 and the moving coil 36 of the induction regulator 14 revolve at. the same speed and the pinion 86 and the gear wheels 84 and 85 maybe soadjusted that the contact arms '24 and 25 move a distance equivalent to the distance between two contact fingers of the selector switch for each revolution of the drum 80 and of the coil 36.

In order to explain the operation of my furnace system, it is assumed that a current below normal value is'flowing through the furnace 1 and it is desired to increase the voltage impressed on the transformer 4. so as to increase the current flow through the furnace. Assuming the contact finger 18 to be engaging the contact segment 17 midway between its extremities, the switch arms-24 and 25 to be in the position illus trated, the movable coil 36 of the induction regulator 14 to be in the position illustrated, and the switch 56 to be in the position illustrated for effecting automatic operation of the system, then the contact arm 64 of the main control magnet 55 will be moved to engage the contact terminal 66 by .reason of the decreased energization of the winding 61. Upon engagement of the contact arm Get with the contact finger 66,

a circuit is completed from the supply conductor 48 through the switch ,arm 57, contact terminal 58, contact arm 65, main contact terminal 66 and the energizing coil of the relay 52 to the supply conductor 49. Thereupon, the relay 52 is operated to "connect the motor 17 across the supply I conductors 48, 49 and 50, in order to operate it in a clockwise direction so as to raise the voltage impressed upon the circuit'of the furnace 1.

The motor 47 effects the rotation of the movable coil 36 of the induction regulator lgthe drum 80 of the transferswitch 11-, and the switch arms 24 and '25 of the selector switch 12, 'but the rotation of the poil 36 is the only operation at this time which produces any lectrical effect upon the circuit of the furnace. I The rotation of the coil 36 increases the voltage of the, primary winding 20 of the auxiliary transformer 13, which is impressed upon the two secondary coils 22 and 23 and, accordingly, increases the voltage which is impressed upon the circuit of former 4. The circuit of the primary winding 5 may be traced from the supply conductor 10 through the switch 68, portion 6 of the winding 5, contact finger 16, contact segments .15 and 17, contact finger 18, second-ary coil 22 of the auxiliary transformer 13, switch arm 24, contact finger 26, the complete portion 8 of the winding 5, and the switch 68 to the supply conductor 9. The voltage impressed on the coils- 22 and 23 is increased until a value equal to one half the voltage existing between 'two adjacent taps primary winding 5 is arrived at and, when the movable coil 21 has been rotated through an angle of ninety degrees. Just previous to the quarter revolution of the coil 36, the switch arm 25 of the selector switch 12 engages the contact finger 31, which is connected to the second transformer tarp 42 and, when' the transfer switch 11 has been rotated through a quarter turn, the switch segment 17 is in engagement with the contact fingers 18 and 19. Accordingly, the twosecondary windings 22 and 23 of the auxiliary transformer 13 are connected in opposition to each other through the transfer switch 11 and the portion 6 of the primary winding 5 to the supply conductor 10, and are directly connected across the transformer taps 37 and 42 by reason of the engagement of the contact arms 24 and 25 with the contact fingers 26 and 31.

Consequently, the current flowing through the primary winding 5 from the supply conductor 10 may pass either through the secondary coil 22 and the primary tap 31 or through the secondary coil 23, which opposes the voltage of the supply circuit by an amount equal to one half the voltage existing between the primary taps 37 and 42, and the transformer tap 42. Upon further rotation of the transfer switch 11, the switch segment 17 becomes disengaged from the contact finger 18 so as to disconnect the secondary coil 22 and the primary tap 37 from the supply conductor 10. Consequently, the supply conductor 10 is connected through the portion 6 of the primary winding 5, the transfer switch 11 and the secondary coil 23 to the second primary tap 42 of the portion 8 of the primary winding 5, with the voltage impressed on the secondary winding 23 opposing the :potential of th supply circuit.

Upon further rotation of the induction regulator 14, the voltage which is impressed upon the secondary winding 23 is gradually reduced to zero value, and the second tap 42 of the primary winding 5 is connected to the supply circuit without the auxiliary transformer 13 adding to, or subtracting from, the voltage of the supply circuit. At this point, the transfer switch 11 and the coil 36 of the induction regulator 14 have effected one half a complet revolution, and further ply of the portion 8 of the rotation of the coil 36 of the induction regulator 14 increases the voltage which is impressed upon the secondary windin 23 of the auxiliary transformer 13 but in such direction as to add to the voltage of the supondary coil 23 is raised to a value equivalent to one half the voltage existing between the primary taps 42 and 38. At this time, the transfer switch 11 and the coil 36 of the induction regulator 14 have effected athreequarter turn, and the contact segment 17 of the transfer switch is in connection with the two contact fingers 18 and 19. Previous to the connection of the contact segment 17 with the contact finger 18, the contact arm 24 of the selector switch 12 has been moved into engagement with the contact finger 27, which is connected to the transformer tap 38. Consequently, the two secondary coils 22 and 23 of the auxiliary transformer 13 are connected in opposition to each other across the transformer taps 42 and 38 so thatthe current from the supply circuit may flow through either of the secondary coils 22 and 23. and either of the ta s 38Iand 42 of the primary winding 5. he further rotation of the transfer switch 11 disconnects the contact segment 17 from the contact finger 19 so as to disconnect the secondary coil 23 and th primary tap 42 from the supply circuit.

Upon further movement of rotation of the coil 36 of the induction regulator 14, the voltage impressed upon the secondary coil 22 is gradually reduced to zero value, as the coil 36 completes a revolution. From the above, it will be noted that, during a com plete revolution of the transfer switch 11 and the induction regulator 14, the connec tion of the supply conductor 10 has been transferred from the primary tap 37 of the portion 8 of the primary winding 5 to the transformer tap 38 so gradually as to pre vent any abrupt circuit changes.

In case the current flowing through the furnace 2 is above normal value, the main control magnet 55 is operated to connect the contact arm 64 with the contact terminal 65 and complete a circuit through the energizing winding of the relay 51. Upon operation of the relay 51, the motor 47 is energized for rotation in a counter-clockwise direction in order to rotate the transfer switch 11, the coil 36 of the induction regulator 14 and the contact arms 24- and 25 of the selector switch 12 in a direction the reverse of that heretofore described. Since the reverse operation. of the selector switch 12, the transfer switch 11 and the induction regulator 14 is similar to the operation of these parts in a forward direction, a detailed description of such operation is deemed unnecessary.

circuit. Upon further rotation of the coil 36, the voltage impressed upon the sec-' In case it is desired to effect manual/ com trol of the furnace 1, the switch 56/is reversedso as to connect the switch blade 57 with the contact finger 59 and transfer the control of the relays 51 and 52 from the main control magnet 55 to the push button switches 53 and 54, the push button 53 serving to operate therelay 51 to increase the voltage impressed upon the furnace,,and the push button 54 serving to operate the relay 1. In a regulator system, an electric furnace, a supply circuit, a transformer for connecting the furnace to the supply circuit, and means, comprising aninduction regulator, for varying the number of effective turns included in said transformer.

2. In a regulator system, an electric furnace, a transformer having aprimary and a secondary .winding, said primary winding 7 having a plurality of taps extending from it and said secondary winding being con-- nected to said furnace, 'a supply circuit, and means, comprising an induction regulator, for governing the connection of the supply circuit to the transformer'taps and for shifting the supply circuit connection from one tap to another tap without any abrupt circuit changes. i

3. In a regulator system, anelectric furnace, 'a supply circuit, a transformer having a plurality of taps extending from it and serving to connect the furnace to the supply circuit, and means, comprising an induction regulator, for changing the connection of the supply to the various transformer taps to maintain the power input into the furnace substantially constant.

4. In a regulator system, an electric furnace, a supply circuit, a transformer having a plurality of taps extending from it and serving to connect the furnace to the supply circuit, an inductio regulator, an auxiliary transformer, and means, comprising said regulator and the auxiliary transformer, for connecting the supply circuit to the various transformer taps without any abrupt cir- .cuit change.

5. In a regulator system, an electric furnace, a supply circuit, a transformer for connecting said furnace to the supply circuit, and means, comprising an inductive device, for varying the number of effective turns included in said transformer to regulate the furnace. v

6. In a regulator system for an electric furnace, a furnace resistor, a supply circuit,

a transformer having a plurality of taps ex tending from it and serving to connect the resistorto said supply circuit, and means, comprisin an induction regulator, for selectively connecting the various transformer taps to the supply circuit to regulate the circuit conditions of said resistor. 7 In 'a regulator system,an electric furnace, a, supply circu1t, a transformer connected to the electric furnace and having a plurality of taps extending from it, means,

.com rising an inductionregulator, for connecting the transformer to the supply circuit, and means for varying the connections of the regulator to the transformer taps to control the furnace and to prevent any sudden changes in' the circuit connections.

8. In a regulator system, a transformer I having a primary and a secondary winding,

a plurality of taps extending from said pri mary winding, an electric furnace connected to said secondary winding, an induction regulator connected to said primary winding and means for varying the connection of said regulator to the transformer taps to regulate the operation of the furnace.

9. In a regulator system, a transformer having a plurality of taps extending from the winding thereof, a supply circuit connected to the transformer, means, comprising an induction regulator, for changing the supply-circuit connections between the various transformer taps, and means for automatically controlling the operation of the inductionregulator in accordance with certain circuit conditions of the transformer. I

10. In a regulator system, a transformer, having a primary and a secondary winding, said'primary winding having a plurality of taps extending from it, a supply circuit adapted to be connected to the transformer, means, comprising an induction regulator, for changing the connection of the supply circuit from one to another transformer tap, and means for automatically operating said induction regulator in accordance with the current flowing in the transformer.

11. In a regulator system, a furnace resistor, a transformer comprising a second: ary winding connected to said resistor, and a primary winding having a plurality of taps extending from it, an induction regu-' ance with the furnace.

13. In a regulator system, a sup 1y circuit, a main transformer having a p. urality of taps extending from it, an auxiliary transformer having a primary winding and a plurality of secondary coils, means for selectively connecting said secondary coils in series with the various transformer taps across the supply circuit, and means, comprising an induction regulator connected to the primary winding of the auxiliary transformer, for varying the voltage of said secondary coils to permit the transfer from one transformer tap to another transformer tap without any abrupt circuit changes.

14., In a regulator system, a supply circuit, an electric furnace, a main transformer connected to said furnace and having a plurality of primary taps, and means comprising an auxiliary transformer and an induction regulator, for connecting the supply circuit to the various taps of the main transformer to control the operation of the furnace without any abrupt circuit changes.

15. In a regulator system, a main trans current flowing through the former having a primary and a secondary winding, a plurality of taps extending from said primary winding, an auxiliary transformer having a primary winding and a secondary winding comprising two coils, means for successively connecting the ,secondary coils of said auxiliary transformer in series with said transformer taps, and means, comprising an induction regulator connected to the primary of said auxiliary transformer, for varying the voltage impressed on said secondary coils to permit the transfer from one transformer tap to a second transformer tap without any abrupt circuit changes.

16. In a regulator system, a main transformer having a plurality of taps extending from the primary winding thereof, a supply circuit, an auxiliary transformer having two floating secondary coils for connecting the supply circuit. to said primary taps, and means for connecting said floating coils jointly in opposition to each other and severally between the supply circuit and the an auxiliary transformer having two secondary windings adapted to be connected in opposition to each other and a primary winding, an induction regulator connected to the primary winding of the auxiliary transformer for varying the voltage impressed on said secondary windings, and means for successively connecting said secondary windings to the primary taps of the main transformer.

18. In a regulator system, the combination with a sup 1y circuit, an electric furnace, a main transformer connected to said furnace and having a plurality of taps extending from the primary winding, and an auxiliary transformer having two floating coils adapted to be connected between said transformer taps and the supply circuit, of means for varyin the voltage impressed on said floating coi s and for varying the connections of the coils to the transformer taps to connect the supply circuit to the various transformer taps and to control the operation of said electric furnace.

19. In a regulator system, a supply circuit, a main transformer having a plurality of primary taps, an auxiliary transformer having two secondary windings and a primary winding, an induction regulator connected to the primary winding of the auxiliary transformer for varying the voltage impressed on the two secondary windings, and means for connecting one of said sec ondary windings between the supply circuit and one of said primary taps, for connecting the two secondary windings in opposition to eachother between two of the primary taps and to the supply circuit, and for connecting the second secondary winding separately between one of the primary winding taps and the supply circuit.

20. In a regulator system, a main transformer having a plurality of taps extending from it, a supply circuit having one side connected to the main transformer, an auxiliary transformer having two secondary windings and a primary winding, means connected to said primary winding of the auxiliary transformer for varying the voltage impressed on the two secondary windings, and means for successively effecting the connection of one secondary winding be tween the supply circuit and one of the primary taps, the connection of the two second ary windings between the two primary taps and to the supply. circuit, and the connection of the second secondary winding separately between a primary tap and the supply circuit.

In testimony whereof, I have hereunto subscribed my name this 11th day of March EDWIN LEHR. 

